1. Field of the Invention
The subject matter of the present invention relates to the use of corrosion inhibitors for nonferrous metals exposed to aqueous systems. More particularly, the present invention relates to a method of prohibiting corrosion of nonferrous metals using 3-amino-5-hydroxyalkyl-1,2,4-triazoles.
2. Description of Related Art
Because of their corrosion resistance, nonferrous metals such as copper and zinc, and alloys of nonferrous metals such as brass and bronze are preferred materials in the construction of water-conveying apparatus such as those used in steam generating plants, heating systems, cooling water circulating systems and the like. These materials are of particular importance for condenser tubes in steam power plants.
Despite relatively good corrosion resistance, analytically determinable amounts of high-grade materials, particularly copper, unavoidably are transferred to the surrounding water in normal use. The copper then deposits downstream on cooling water pipes made of steel or other base materials causing pitting corrosion sometimes with disastrous results.
For this reason, water contacting nonferrous metals must be treated in order to avoid the consequences of this metal, e.g., copper, transfer. In practice, very few inhibitors are suitable for this purpose. Suitable inhibitors include mercaptobenzthiazole, benzotriazole, tolyl triazole and benzimidazole. While these compounds are relatively effective copper corrosion inhibitors, they have the great disadvantage of being difficult, and hence expensive, to produce. Therefore, they have found only limited application.
Another disadvantage of the above-mentioned compounds is their poor solubility in acidic aqueous solutions, so that preparation and packaging of commercial aqueous anticorrosion preparations and especially concentrated anticorrosion preparations involves great difficulties. Moreover, concentrates of these materials tend to be unstable over extended periods of time, and these compounds and their derivatives have a high toxicity. Thus, these materials cannot be used in certain fields of application.
U.S. Pat. No. 4,298,568 discloses the use of 3-amino-5-alkyl-1,2,4-triazoles for inhibiting the corrosion of nonferrous metals in industrial water systems. Although these compounds are easier to produce and have better properties with respect to their technical applications, there still is a need in the art for an improved corrosion inhibitor for nonferrous metals in contact with aqueous systems.
It is an important object of the present invention to provide methods of chemically inhibiting corrosion of nonferrous metals with corrosion inhibitors having not only good applicational properties, but also providing a high degree of corrosion protection, even at low corrosion inhibitor concentrations. It is another important object of the present invention to provide a method of inhibiting corrosion utilizing corrosion inhibitors which can be stored as concentrates over extended periods of time without loss of activity.